package cn.edu.scau.cmi.suwenpeng.chapter07;
interface A4{
	double f(double x,double y);
}
class B4 implements A4{

	@Override
	public double f(double x, double y) {		
		return x*y;
	}
	int g(int a,int b) {
		return a+b;
	}
	
}
public class E_exercise4 {

	public static void main(String[] args) {
		A4 a=new B4();
		System.out.println(a.f(3, 5));
B4 b=(B4)a;
System.out.println(b.g(3, 5));
	}

}
